Industry has produced semi-flexible or flexible phenolic foams having a substantially open cellular structure. The foams are the reaction product of a mixture of a phenol-aldehyde resin, a surfactant, a blowing agent; optionally a wetting agent and a catalyst. The method for producing a semi-flexible or flexible phenolic foam composition having a substantially opened cellular structure comprises mixing a phenol-aldehyde resin with a surfactant, a blowing agent and optionally a cell opening and wetting agent; curing the mixture by reacting it with an acid catalyst; compressing the cured or semi-cured product below its original thickness and releasing the pressure, thereby obtaining the desired semi-flexible or flexible phenolic foam composition.
U.S. Pat. No. 5,057,546 discloses such a semi-flexible or flexible phenolic foam composition. This foam composition is a substantially open cellular structure. Open cell phenolic foams have about half the R value of closed cell phenolic foams. The open cell foams are intended for conventional insulation uses, fluid absorption, sound absorption cushioning and the like. The open cell foams are not intended for pipe insulation.
Other prior art processes typically spray a liquid on the pipe which foams in place to produce foam insulation. The liquid systems are difficult to use and must be used on site immediately. For example, U.S. Pat. No. 5,292,464 discloses thermally insulating storage tanks or water heaters. The invention uses a jacket which forms a hollow insulation space where a liquid foam insulation is injected into the space. This is the conventional way of foaming in place. U.S. Pat. No. 5,405,665 shows another conventional foam in place pipe insulation. Multiple non-foam layers and foam layers are used. This pipe insulation is a multi-layer foam, heat shrinkable tube which also uses a hot melt adhesive. The use of hot melt adhesives presents another complicating step in production.